1. Field
The present invention relates to a heat dissipation device for use in removing heat from electronic devices, and more particularly to a heat dissipation device incorporating a heat pipe for improving heat dissipation efficiency of the heat dissipation device.
2. Prior Art
During operation of an electronic device such as a computer central processing unit (CPU), a large amount of heat is often produced. The heat must be quickly removed from the electronic device to prevent it from becoming unstable or being damaged. Typically, a heat dissipation device is attached to an outer surface of the electronic device to absorb heat from the electronic device. The heat absorbed by the heat dissipation device is then dissipated to ambient air.
Conventionally, a heat dissipation device comprises a solid metal base attached on the electronic device, and a plurality of fins arranged on the base. The base is intimately attached on the electronic device thereby absorbing the heat generated by the electronic device. Most of the heat accumulated at the base is transferred firstly to the fins and then dissipated from the fins. However, since the electronics technology continues to advance, amount of the heat generated by the electronic devices increases enormously. Many conventional heat dissipation devices are no longer able to efficiently remove heat from these electronic devices.
In order to overcome the above disadvantages of the heat dissipation device, one type of heat dissipation device used for the electronic device includes a heat pipe which can quickly transfer heat from a position to another position of the heat dissipation device. A heat pipe is a vacuum-sealed pipe that is filled with a phase changeable fluid, usually being a liquid, such as water, alcohol, acetone and so on, and has an inner wall thereof covered with a capillary configuration. As the electronic device heats up, a hot section usually called evaporating section of the heat pipe, which is located close to the electronic device also heats up. The liquid in the evaporating section of the heat pipe evaporates and the resultant vapor reaches a cool section usually called condensing section of the heat pipe and condenses therein. Then the condensed liquid flows to the evaporating section along the capillary configuration of the heat pipe. This evaporating/condensing cycle repeats and since the heat pipe transfers heat so efficiently, the evaporating section is kept at or near the same temperature as the condensing section of the heat pipe. Correspondingly, heat-transfer capability of the heat dissipation device including such the heat pipe is improved greatly.
As disclosed in China patent No. CN 2599756Y, a heat dissipation device comprises a heat pipe thermally contacting a base for absorbing heat from a heat generating electronic device and a plurality of fins for dissipating the heat. However, due to small thickness of each fin, the heat pipe has a very limited area contacting the fins. Additionally, it is difficult to achieve intimate combination between the heat pipe and the fins. As a result, the heat exchange between the fins and the heat pipe is considerably limited. Furthermore, the fins can not be stably stacked on the heat pipe due to the same reason. TW patent No. 547002 discloses another heat dissipation device comprising a heat pipe combined to two heat sinks. The heat pipe is substantially U-shaped, and comprises two parallel portions and a middle portion connecting the two parallel portions. The two heat sinks are disposed to have fins thereof face to face and two rectangular bases thereof positioned at top and bottom sides of the fins. The two parallel portions of the heat pipe are respectively combined to the two bases of the two heat sinks. In use, heat generated by the electronic device is absorbed by the base of one heat sink contacted thereto, then delivered by the heat pipe to the fins and the base of the other heat sink to be dissipated to ambient air. However, the heat pipe only has the two parallel portions combined to the heat sinks, such that contacting area of the heat sinks and the heat pipe is still small; thus, the heat pipe is not fully utilized. So, with development of computer industry, the heat dissipation device needs further improvement to meet with high heat dissipating demand of the electronic device. In the meantime, it is preferred that the heat dissipation device has a low cost. Metal extrusion is a method for forming a heat sink with a low cost. Furthermore, it is desired that when an electric fan is used, an airflow generated by the electric fan can smoothly flow through fins of the heat sink to effectively take heat away from the heat sink.